This invention relates to pillared clays, to their production and to their use.
Edible oils such as vegetable, animal or fish oils generally contain a variety of constituents which detract from their stability, appearance, taste or smell or which may represent a health hazard for consumers. Examples of such impurities are pigments such as the carotenoids or the chlorophylls, phosphorus compounds such as the phospholipids or phosphatides, and polyaromatic hydrocarbons such as benzo(a)pyrene. Some of these impurities, for example polyaromatic hydrocarbons or porphyrin-type materials such as chlorophyll, have relatively large molecular dimensions which can hinder their removal from oil or other liquids by adsorption onto a solid removable adsorbent material.
Pillared clays, while in general possessing desirable molecular sieve charcteristics as adsorbents, show relatively poor ability to adsorb porphyrin-type molecules from oils. The present invention relates more specifically, however, to pillared clays which show substantial ability to adsorb such molecules from oils, to a method for producing such pillared clays and to a process for the purification of oils using such pillared clays.
The removal of chlorophyll or other impurities from soyabean oil using acid activated montmorillonite is discussed by D. R. Taylor et al in a paper published in JAOCS, Vol 66, No. 3, March 1989. In that paper pillared montmorillonite produced from non-acid-activated clays was shown to have a low activity, in the adsorption of chlorphyll. On treatment of the already pillared clay with sulphuric acid the chlorophyll removal activity decreased still further.
It has now been found that pillared clays produced by introducing pillars into a previously acid-activated clay can be effective adsorbents for use in oil purification, and can show a substantial ability to remove chlorophyll from the oils.